The present invention relates to a method of manufacturing a rolling bearing device for a wheel, particularly a method of manufacturing a rolling bearing device for a wheel that rotatably supports a wheel to a suspension system of a vehicle.
In general, in rolling bearing devices for a wheel, a rolling bearing is mounted around the outer circumference of a hub shaft connected to a wheel through a flange at one axial end in such a manner that the bearing is prevented from being axially slipping off.
Such a hub shaft has a cylindrical end for retaining the rolling bearing at the other axial end (the right in FIG. 8). The cylindrical end is bent radially outward by an exclusive caulking jig and caulked as a caulked portion to the outer circumference of the inner ring of the rolling bearing. The rolling bearing does not slip off the hub shaft and receives pre-pressure by the caulked portion.
According to the caulking process, referring to FIG. 8A, when caulking load P is applied radially inward to a cylindrical end 1e of a hub shaft by a caulking jig, as shown in FIG. 8B, a caulked portion 1f is formed. Therefore, the end 1e of the hub shaft is made of steel, such as S55C, which is easy to apply plastic forming, to facilitate caulking process.
In a rolling bearing device for driving wheel of a vehicle, spline teeth 1c that are engaged with a shaft mounted at the outer ring of a constant velocity joint of a joint member are formed around the inner circumference of a through hole formed through the hub shaft.
According to the rolling bearing device for a wheel, as shown in FIG. 8B, large moment exerts in the cylindrical end of the hub shaft by the caulking load P generated in the caulking process, which may cause radially inward plastic deformation (radial contraction) of the through hole. When the radial-inward deformation of the through hole is large, the inner diameter of the spline teeth 1c (spline portion) is deformed and it is difficult to insert the shaft, so that it is required to apply broach process to the through hole of the hub shaft to adjust the dimensions, after the caulking process. It increases the number of processes and manufacturing cost. Further, because a clearance is formed between the end and the inner ring of the rolling bearing by the radially inward plastic deformation of the through hole, the bearing rigidity of the bearing device is deteriorated.
For this reason, to prevent plastic deformation of the end of the hub shaft, a method of caulking the end with a column-shaped metallic jig that is engaged with a portion of a region of the through hole corresponding to the region where the rolling bearing is mounted has been proposed (see JP-A-2002-301532).
According to the caulking method disclosed in JP-A-2002-301532, it has an effect on preventing inward plastic deformation of the through hole. However, since engaging with the through hole of the hub shaft is made by pressing the column-shaped jig, it is difficult to insert/extract the column-shaped jig into/out of the hub shaft before/after caulking process. Accordingly, the column-shaped jig may damage to the spline portion of the hub shaft.